No abstract

Disposable diapers have become a prominent feature of solid waste dumped in landfills. It is estimated that disposable diapers take anywhere between 300 to 500 years to decompose. Despite the associated environmental challenges, a plethora of studies show that disposable diapers have become a popular choice for parents when compared with cloth diapers. Disposable diapers are argued to be more convenient for parents because of their once-off use and super-absorbent ability, of which they are able to absorb 200-300 times the weight as compared to the cloth diapers. This study investigates thermal devolatilisation profiles of disposable diapers as well as their iso-conventional kinetic parameters, elemental and fractional composition. In this study, the two most dominant disposable diaper brands were sampled and analysed qualitatively and quantitatively. It was observed that the exterior fraction of both diapers showed a single peak devolatilisation at a temperature of around 500°C, while the interior fraction showed two distinctive devolatilisation peaks observed below 400°C and above 500°C. However, the pyrolysis heating rate produced no effect on the pyro-char fraction. Furthermore, the devolatilisation pathways of different types of disposable diaper fractions showed that there is a potential for conducting stepwise pyrolysis to promote fractional recovery of valuable products. Disposable diapers waste conversion can be better handled by separating the outer fraction (mainly fossil-based plastics and rubbery materials) from the inner fraction (mainly bio-based fibers and absorbents). It is further illustrated that the kinetic parameters, Ea and k0 are different for each disposable diaper fraction.

Seven disposable diaper brands that are commonly used in Clermont, Kwa-Zulu Natal (South Africa) and some frequently found along river bodies (due to illegal dumping) were characterised through proximate analysis, thermogravimetric analysis (TGA), ultimate analysis and analytical pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS). A novel approach entailing separation of the diapers into two fractions, interior (constituting mainly biomass fibres) and exterior (mainly constituting non-biomass polyethylene), assisted in assessing thermochemical conversion of the disposable diaper’s potential as well as likely threats to the environment. In a comparison of the volatile matter between the two fractions, the exterior fraction is more combustible (due to a higher volatile fraction). Hence, it is more suitable for energy recovery. The present study investigates the use of pyrolysis to manage disposable diapers to potentially recover pyro-oil, pyro-gas and pyro-char. In this primary investigation, it was observed that each disposable diaper brand reacts differently to constant heating. However, the proximate and elemental analysis also highlights the likely negative environmental threats, such as that the high volatile content can potentially release dangerous permanent gases such as chlorine and cobalt into the atmosphere after the diaper is disposed of illegally and in landfill.

Informal waste pickers in cities across the Global South divert significant amounts of tonnage from landfills. This diversion contributes towards a sustainable environment and better public health practices. Informal workers globally derive livelihoods from collecting, sorting, and selling recyclable waste. In South Africa, there is growing recognition of the valuable work that waste pickers carry out. Despite this, however, these informal workers remain largely unrecognised, are often stigmatised, and suffer from a lack of social protection linked to their work. This lack of recognition and protection creates specific occupational hazards for waste pickers. Using an ethnographic method, this study explores the physical and socio-psychological hazards that emerge from waste picking on the streets of the inner city of Durban, in South Africa. We found that the waste pickers, the majority of whom were women, developed mitigation strategies against these risks. A better understanding of how the occupational hazards of waste picking are shaped by the local context of working on the street enables the recognition of the knowledge waste pickers already hold regarding mitigation strategies. Insight into occupational hazards are important to consider if the municipal integration of waste pickers is to happen in a way that ensures access to social protections for these informal workers.